One of the most ubiquitous and well-recognized weapons, the AK-47 rifle was designed and entered service in the mid to late 1940s. The designer, Mikhail Kalashnikov, also designed the AK-74 (variants of which are still being produced), which shares numerous parts with the AK-47 and its variants. The typical configuration for the Kalishnikov firearms include a rear trunnion fitting configured to interface with a fixed (non-folding) stock.
To ensure modularity and compatibility with various stock configurations including, for example, fixed stocks, side-folding stocks, and under-folding stocks, the firearm may be designed with a different rear trunnion fitting and/or a new folding hinge fitting.